Acoustic vaporization of droplet aggregations

Acoustic Droplet Vaporization (ADV) is a phenomenon wherein micron- and sub-micron-sized droplets are vaporized into microbubbles upon exposure to high-frequency ultrasound. This process can be used to improve the contrast in medical ultrasound imaging and for targeted drug delivery in the human body. Here, we investigate droplet aggregations as a way to reduce the acoustic pressure required to achieve ADV compared to single droplets. We perform experiments on different droplet aggregations using ultra-high-speed video-microscopy to temporally resolve their vaporization dynamics upon acoustic excitation. The phenomenon discloses rich dynamics – from the nucleation of micro-cavitation in a specific droplet within the aggregation to the full vaporization of the droplets. We compare the dynamics of aggregations to those of individual droplets and discuss their implications in reducing the vaporization threshold of ADV.